She blew on or in his face?

Question

This dictionary says

blow: 2 a : to create a current of moving air by breathing

[no object]

She blew on her fingers to warm them.

He was blowing on his soup to cool it off.

[+ object]

She blew air into the balloon.

But other dictionary says

blow: 3 AIR FROM YOUR MOUTH [intransitive, transitive always + adverb/preposition] to send air out from your mouth

blow (something) into/onto/out etc

She blew onto her coffee to cool it down.

He blew the smoke right in my face.

So, we say:

She blew on or in his face?

Answer 1

Blowing air at a persons face is a very rare action.

If you "blow in his face" it suggests an annoying action. We could also say "She threw a cup of water in his face". If you blow smoke at someone it is nearly always annoying: nobody wants to breath your smoke.

On the other hand "blow on his face" could be to warm it, or as a lover's game. It is a gentle action. You need to be quite close to someone and the situations where this would happen are rare. On the other hand, it is quite common to blow on your own hands.

Mary was so angry she was speechless. She walked right up to John and blew right in his face. Then she turned and walked out the door. She hated him so much.

...

Mary lay beside John, kissing and blowing on his face and body. He giggled as she ticked him. She loved him so much.

Answer 2

The neutral word here is on: we blow on (or onto) things unless we are definitely blowing inside them (eg a balloon, or somebody's mouth when giving them resuscitation).

But in somebody's face is the word we use when we talk about doing something to somebody via their face: blowing, hitting, spraying, smiling, shouting.

If we are talking about applying make-up, we might talk about putting foundation on their face, because this is treating the face as an object. But when we do something to the face as a way of interacting with the person, in the face is more usual.